S-Pisces 2B Version 5.0 Arrives


A. Strachan, Dr. Y. Apanovich, Dr. E. Lyumkis, Dr. B.Polsky, A. Shur, Dr. A. Tchernaiev, Dr. P. Blakey, and Dr. I. Pesic


S-Pisces 2B Version 5.0 contains many new features requested by customers. Enhanced algorithms increase speed and improve convergence. The new features of S-Pisces 2B Version 5.0 include:


Additional Physical Models

  • Models for floating gate simulations of EPROM and EEPROM devices based on improved charge boundary conditions.
  • Gate current models for both electrons and holes.
  • Self-consistent Fowler-Nordheim tunneling model (The Simulation Standard, January, 1992).

Capabilities for Breakdown Analysis

  • Ionization integral calculation.
  • Electric field line plotting.
  • Automatically stop voltage ramps using compliance limits.
  • Option to save the last valid solution to a bias ramp.
  • Enhanced continuation methods allow tracing snapback curves in a single input deck.

Added Circuit Elements

  • Inductors are supported as external circuit elements.

UTMOST III Interface

  • UTMOST III extensively models and analyzes data produced by S-Pisces 2B.


This is the final link in the path from our process device SPICE modeling SPICE environment.

  • Interface to TonyPlot for displaying s, y, z, and h small signal parameters.
  • The automatic interface supports input of doping profiles from SSuprem3 or 1D SSuprem4 and 2D doping profiles from SSuprem4 .

Keyword Selection of Models

  • Normally used models for MOS, bipolar, and EEPROM programming and erasing can be selected using one keyword (e.g., models bipolar). This capability is especially useful for first-time S-Pisces 2B users.

Electrode Capabilities

  • The maximum number of electrodes has been increased to 20; additional models are available at customer request.
  • Electrodes can be named and subsequently referred to by name rather than number. The name is used automatically in graph labels and in the UTMOST III interface.
  • Electrodes can be slaved; i.e., the bias conditions on one electrode can be specified as a function of the conditions on other electrodes.


Improved Speed and Convergence

We have taken the broad approach of improving discretization techniques, iteration strategies, initial guess strategies, and increasing the calculation accuracy of certain matrix elements. These improvements increased speed (sometimes by a factor greater than two) and made convergence for difficult calculations less grid-dependent.


Example 1: Inductors

The ability to specify inductors as external circuit elements is very important to designers of power devices and circuits. Figure 1 illustrates the transient voltage on the contact of a power diode during a turn-on pulse with a 0.15µH inductor. These results show the effect of impact ionization caused by the large induced voltage.

Figure 1. Inductive Ringing Calculation.


Example 2: Continuation Methods

Using older PISCES to simulate snapback and other negative resistance curves, it is necessary to use voltage boundary conditions for simulation up to the breakdown point and then apply current boundary conditions beyond breakdown to trace the rest of the curve. S-Pisces 2B version 5.0 automatically detects the breakdown point and either switches boundary conditions and continues or terminates execution, as the user specifies. The criterion for halting the voltage ramp may be based on evaluation of ionization integrals or analysis of I-V curve gradients. These methods are easy to understand and provide a reliable way of detecting the breakdown point.

Figure 2 is a snapback simulation of an 0.8µm channel length LDD MOSFET with a gate voltage of 1.0V. One input deck, which contained no information about the value of the breakdown voltage, generated the complete simulation.

Figure 2. Automated Snapback Calculation.


Example 3: UTMOST III Interface

Figure 3 shows S-Pisces 2B I ID/VDS data for a 10/1 NMOS LDD device imported by UTMOST III. Simulated data from S-Pisces 2B is treated as measured data. UTMOST III can curve fit, optimize, or simulate imported curves to a selected SPICE model. S-Pisces 2B currently supports MOS, Bipolar, and diode routines.

Figure 3. UTMOST III simulation from S-Pisces 2B data.



S-Pisces 2B Version 5.0 includes many new features. It runs faster and converges more reliably. We have pushed it into the position of industry leader and we are steadily evolving it into PISCES 3, the new industrial device simulator standard.